This application claims the benefit of Korean Application No. 97-41285, filed Aug. 26, 1997, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an audio encoding/decoding apparatus, and more particularly, to an audio encoding/decoding apparatus for providing higher quality audio than the quality provided by a digital versatile disc (DVD)-video standard. The present invention also relates to a DVD for recording/reproducing audio information by adding a recorder to an audio encoding apparatus and adding a reader to an audio decoding apparatus.
2. Description of the Related Art
There have been various compression techniques for efficiently transmitting and storing information such as video or audio data, which are classified into a lossless encoding method in which restored data is the same as original data which is not compressed and a lossy encoding method in which data loss occurs by compression and restoration. The lossless encoding method and lossy encoding method are used to provide high quality audio signals.
An existing lossless encoding method usually varies a compression rate according to data properties and compresses data according to the varied compression rate. Therefore, a transmission rate of bitstreams produced by compression does not become consistent. The lossless encoding method cannot restrict a bit rate to a constant value. Accordingly, if a bit rate is restricted compulsively, a loss of information occurs due to the limit of the bit rate. In other words, a constant bit rate does not mean lossless information.
Meanwhile, an existing lossy encoding method using an acoustic psychology analyzes an audio signal in order to remove an unnecessary portion and a lossy element of data and lower an accuracy for a less significant signal, and compresses the audio signal based on the analysis. The lossless encoding method can compress a signal into a constant bit rate. However, since a prior-to-being-compressed signal differs from a signal obtained by reproducing a compressed signal, it is difficult to reproduce an audio signal into a high quality audio signal. Particularly, in the case when an audio signal is compressed over the whole bands of the audio signal using an acoustic psychology, although a bit rate is sufficiently given, a loss of information occurs even in a fundamental band to which information which should be transmitted without any loss in view of a physiological sensation.
To solve the above problems, it is an object of the present invention to provide an encoding apparatus for compressing a high quality audio signal into a constant bit rate, using a combination of a psycho-acoustical encoding method which is an existing lossy coding method and an existing lossless coding method.
It is another object of the present invention to provide a decoding apparatus for restoring an audio signal encoded by the above encoding apparatus.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To accomplish the above and other objects and advantages of the present invention, there is provided an audio encoding apparatus including separation means for receiving a digital audio signal and separating the received digital audio signal into a first audio signal belonging to a first region and a second audio signal belonging to a second region, in which the whole audio region represented by the received digital audio signal is divided into the first and second regions; lossless encoding means for lossless encoding the first audio signal and outputting a first bitstream and a first bit rate possessed by the first bitstream resulting from the lossless encoding; and psycho-acoustical encoding means for psycho-acoustically encoding the second audio signal and outputting a second bitstream and a second bit rate possessed by a second bitstream, in which the second bit rate is a difference between a predetermined bit rate and the first bit rate.
There is also provided an audio decoding apparatus including an input port for receiving a first bitstream generated by losslessly encoding a digital audio signal belonging to a first region and a second bitstream generated by psycho-acoustically encoding a digital audio signal belonging to a second region, in which the sum of a first bit rate possessed by the first bitstream and a second bit rate possessed by the second bitstream is a predetermined bit rate and the whole audio region is divided into the first and second regions; lossless decoding means for losslessly decoding the first bitstream received via the input port and thus generating a first audio signal belonging to the first region of the whole audio region; psycho-acoustical decoding means for psycho-acoustically decoding the second bitstream received via the input port and thus generating the second audio signal belonging to the second region among the whole audio region; and combining means for combining the first and second audio signals and outputting the combined result.